Recently in the field of semi-conductors, a lead titanate zirconate (PZT) film, a barium strontium titanate (BST) film, a tantalic acid strontium bismuth (SBT) film, a titanic acid zirconate lantern lead (PLZT) film, etc., each having a high dielectric constant and also a high step coverage has been used as an oxide-based dielectric film for a semiconductor memory. In regard to the CVD material for the foregoing thin films, for example, Pb(DPM)2 (solid material) as a Pb source; Zr{OC(CH3)3}4 (liquid material) and Zr(DPM)4 (solid material) as Zr sources; Ti{OCH(CH3)2}4 (liquid material) and Ti(OCH (CH3)2)2 (DPM)2 (solid material) as Ti sources; Ba(DPM)2 (solid material) as a Ba source; and Sr(DPM)2 (solid material) as a Sr source are employed.
A liquid material, when being used as a CVD material, is usually introduced into a vaporizer along with a carrier gas via a flow rate controller, and the mixed gas is made into a gaseous form in the vaporizer and thereafter is fed to a CVD apparatus. However, it is difficult to vaporize a liquid material at a desirable concentration and flow rate in high efficiency without deteriorating the quality thereof, since the liquid material has usually a low vapor pressure, a high viscosity and a vaporizing temperature close to a decomposing temperature.
A solid material, although being capable of assuring highly pure material by being kept at an elevated temperature to sublime itself, makes it extremely difficult to assure sufficient supply amount in an industrial scale. Thus, in general it is dissolved in a solvent such as tetrahydrofuran to make it into a liquid material so as to vaporize. However, since a solid material has a vaporizing temperature greatly different from that of a solvent, a solvent alone is more apt to vaporize by heating, thereby making it more difficult to vaporize a liquid material.
Such being the case, highly advanced technique is required for manufacturing an insulated thin film by using a material in liquid or solid form. Conversely, an insulated thin film having high quality and high purity is expectable by the use of a liquid material or solid material. Accordingly, a variety of vaporizers and apparatuses for vaporizing and supplying have been developed for the purpose of efficiently vaporizing the aforesaid material without deteriorating the quality thereof.
For example, U.S. Pat. No. 6,473,563 B proposes a vaporizer wherein at least a portion of a CVD material feed portion in contact with a CVD material is constituted of a corrosion resistant synthetic resin; and an apparatus for vaporizing and supplying which comprises a cooler and the vaporizer wherein the inside of the CVD material feed portion of the vaporizer and the surface on the side of the vaporization chamber of the CVD material feed portion are constituted of a corrosion resistant synthetic resin; the feed portion in contact with the outside of the vaporizer is constituted of a metal; and the CVD material feed portion which is constituted of a metal and which undergoes heat transfer from the heating means upon heating the vaporization chamber can be cooled with a cooler. It is a vaporizer in which at least a portion of the CVD material feed portion in contact with the CVD material is constituted of a corrosion resistant synthetic resin which has not only heat resistance but also heat insulating property and characteristics of less liability to adhesion of the CVD material.
The use of the foregoing vaporizer enabled, even in the case of using a solid CVD material dissolved in an organic solvent as a CVD material, only the material to be vaporized with an efficiency of 99.9% or higher because any abrupt heating was prevented without generating any deposit of the material accompanied with adhesion thereof. In addition, the foregoing apparatus for vaporizing and supplying is equipped with a mechanism for cooling the CVD material feed portion at the time of heating the vaporization chamber, and the apparatus was least liable to the adhesion of deposits.
However, although the foregoing vaporizer and apparatus for vaporizing and supplying have effects of preventing the generation of any deposit of the solid CVD material accompanied with adhesion inside the CVD material supplier, a decrease in a feed amount of a carrier gas to be supplied accompanying the CVD material brings about such disadvantage that a solvent alone is vaporized, in the same manner as the conventional vaporizers, thus causing an anxiety of a solid CVD material to be more prone to be deposited in the vaporizer. On the contrary, it is desirable to improve use efficiency by supplying the CVD material having high concentration in chemical vapor deposition.